The present invention relates generally to evaporators, and in particular to defrost operations associated with evaporators.
Evaporators are commonly employed as part of a refrigeration system, wherein the evaporator converts a liquid refrigerant to a gas, thereby absorbing heat and providing cooling. In some applications, the refrigerant employed by the evaporator operates at a temperature below the freezing point of water. As a result, cooling fins on the evaporator through which the refrigerant flows may cause water vapor in the air being cooled to condense and freeze as it passes through the evaporator. As a result of the freezing water vapor, ice forms on the outside surface of the cooling fins, causing them to “plate out”. This buildup of ice reduces the efficiency of the evaporator. In addition, as ice builds up on the fins, the load on the compressor drawing refrigerant through the evaporator decreases, causing the refrigerant temperature to fall even further and thereby causing ice to form more quickly.
In response, refrigeration systems periodically employ a defrost operation to melt the ice build up on the fins of the evaporator. Typically, the defrost operation is implemented on a periodic schedule (e.g., every hour, day, etc.). However, there are a number of drawbacks to employing purely periodic defrost operations, such as running the defrost operation when none is required (lowering efficiency of the system), or running the defrost operation too late, such that the defrost operation is insufficient to melt the build-up of ice.